Cook County Commissioner Forrest Claypool and Board of Review Commissioner Joseph Berrios unleashed negatives TV ads this week, as the two well-funded candidates are locked in a bitter battle in the race for assessor.

The two are Democrats, but Claypool is running as an independent, while Berrios, who is also chairman of the Cook County Democrats, is the formal party nominee after winning the February primary. Neither ad addresses fellow opponents Robert Grota of the Green Party and Republican Sharon Strobeck-Eckersall.

Berrios has admitted to accepting contributions from property-tax attorneys who argue assessment appeals before the Board of Review, and it's simple math to understand that, when someone is granted a reduction, other property taxpayers end up having to pay more as the tax burden is spread out.

"The one problem is the causal connection," said Professor Dick Simpson, head of the political science department at the University of Illinois at Chicago. "The fact that he took the campaign contribution, did that cause him to decrease their property taxes?"

Berrios has insisted no and that his office has never been charged with a crime.

"Of course, it is a conflict of interest," Simpson added. "He would be better off setting a rule."

Berrios had no vote on the matter, in that he was not a member of the county board, but Berrios campaign manager Kelley Quinn allowed that as head of Cook Democrats he did go on the record saying he approved "if drastically needed to support the hospital and health care agencies."

Claypool did oppose the increase and led the fight for its partial repeal earlier this year.

While Claypool has run as a progressive reformer on the county board, and obviously as an independent for assessor, he did previously serve as Chicago Mayor Richard M. Daley's chief of staff and as head of the Chicago Park District.

Cook Clerk David Orr, a fiercely independent Democrat, recently said Claypool had been both an insider and an outsider, and pointed to how he himself could have been considered an insider while allied with Chicago Mayor Harold Washington in the city council in the '80s.

"City Hall insider Claypool cut a deal to let a private, for-profit company run parking garages," the commercial added.

Claypool spokesman Thomas Bowen called that "total bunk," saying the deal to privatize Grant Park garages was in place before Claypool became CPD. superintendent in 1993. Claypool did, however, support the privatization, as did Erma Tranter, then executive director of Friends of the Parks and now president of the watchdog advocacy group.

The Berrios ad went on: "Claypool was paid thousands in campaign cash, while we paid more in parking fees."

Again, Simpson said, there's a lack of any formal causal connection, and Bowen added it was "laughable," in that Claypool received a campaign contribution from Standard Parking 10 years later when running for the county board.

"Claypool gave out huge pay raises, ignoring a county pay freeze while we pay higher taxes," the ad charged.

Yet Claypool explained, before the county board, that he actually promoted one aide to chief of staff with the position open, then left the aide's earlier post unfilled, actually saving the county money.

Simpson said there were benefits for Claypool in pointing out chinks in Berrios' record, but that the mudslinging might serve Berrios better overall, seeing as he's already been tainted by a Better Government Association article charging conflicts of interest that ran in Chicago magazine.

"It is to Claypool's interest that more voters know these stories," Simpson said, "but if Berrios can discredit Claypool then maybe they just won't vote or the (Democratic) machine vote will be sufficient to carry Berrios in.

"Berrios isn't going to increase his vote," he added, "but he can reduce Claypool's."